This invention involves recognition of the fire hazard presented by electric panel cabinets housing main electric service panels or subpanels for the electric supply to a building. Electric panel cabinets contain many components that can overheat and start fires; and these include: feeder conductors, branch circuit conductors, main circuit breakers, branch circuit breakers, and bus bars. The overheating of electrical components within an electric panel cabinet can be caused by loose or corroded connections or power overloads and can ignite a fire in the cabinet, which can spread to nearby building components.
Smoke alarms, which are required by the majority of local building codes throughout the United States, are not adequate protection against fires started in electric panel cabinets. The smoke alarms may not be located near the electric panel cabinet; and even if they are, they actuate only after a fire is sufficiently established to produce smoke. Smoke alarms are also required to be powered by the building's electrical service; and a fire started in an electric panel cabinet can cause a loss of electrical power after the fire is started, which would disable the typical smoke detector.
High temperature alarms have been suggested for purposes other than electric panel cabinets. These include the stovepipe alarm suggested in U.S. Pat. No. 4,866,427 and the safe alarm suggested in U.S. Pat. No. 5,072,211. Also, high temperature responsive shutoff switches have been suggested for shutting off overheated appliances.
We have found no evidence that high temperature alarms have been suggested for electric panel cabinets, though. We have also found that applying an alarm to an electric panel cabinet involves special problems because of the power supply components that it houses and the possibility of a power failure when an alarm is required.